Sensors for the high resolution astronomical imaging

Abstract

Optical interferometry with single aperture, as well as with multi-aperture require high quality sensor that enables to obtain snap shots with a very fast time resolution of the order of (i) frame integration of 50 Hz, or (ii) photon recording rates of a few MHz. Although advancement of real time compensation of atmospheric turbulence using adaptive optics (AO) system has made inroad in obtaining diffraction-limited astronomical imaging (mostly in infrared wavelength), it needs high time resolution cameras. The performance relies on the characteristics of such sensors, e.g., (i) the spectral bandwidth, (ii) the quantum efficiency, (iii) the detector noise that includes dark current, read-out and amplifier noise, (iv) the time lag due to the read-out of the detector, and (v) the array size and the spatial resolution. Until recently, micro channel plate Based intensifier is added before a CCD to gather the speckles or fringes of faint objects. Recent development of the solid state based non-intensified low light level CCD (L3CCD), which effectively reduces readout noise to less than one electron RMS has enabled substantial internal gain within the CCD before the signal reaches the output amplifier. After a brief presentation on the interferometry and adaptive optics system, the current trend and future progress in developing new generation optical/IR sensors will be discussed.